The invention relates to a continuous casting plant with rollers or rolls for supporting, guiding, bending, straightening and deforming a wide continously cast strand, in particular a steel slab with a width of more than 1,000 mm.
In the continuous casting of steel strands, in particular in the casting of slabs with widths of 1,000 to 2,500 mm, underneath the water-cooled mould numerous supporting rollers have to be arranged as close to one another as possible, in order to inhibit a bulging of the strand skin caused by the ferrostatic pressure of the liquid core of the strand. It has been shown in practice that such deformations of the strand skin, in particular when rollers with relatively wide diameters are used, lead to cracks and thus to a lessening of the quality of the cast product. The problem of the supporting of the strand skin becomes especially critical when a high casting speed (extraction speed of the strand) is necessary. Such so-called rapid casting plants with a casting speed of more than about 1.2 m/min, e.g. with 1.6 to 2 m/min, require special care in the construction and maintenance of the whole supporting and guiding roller construction, since with an increasing casting speed the need for precise support of the strand increases and the extraction force on the cast strand increases accordingly.
Known continuous casting plants have the disadvantage that the cooling is effected exclusively by the spraying of cooling water onto the strand from the outside. When the spraying nozzles are out of order, e.g. when they are clogged by impurities, there is the danger of over-heating so that on the rollers and in the bearing elements, temperatures of more than 700.degree. C can occur which cause the bearing grease to coke and the bearing to become blocked. Furthermore, when such a disturbance occurs, a high increase in the extraction force is necessary, which may lead to cracks.
Further difficulties in known plants arose due to the fact that the individual rollers arranged adjacent one another could not be driven for reasons of construction, and therefore the extraction forces were applied to the strand by special driving strands with rolls having wide diameters. When a number of drive stands are arranged at intervals between the non-driven supporting rollers, the danger of undue expansions of the strand skin exists at the transition places.
In order to overcome such difficulties, a proposal not yet belonging to the prior art consists in that the rollers or rolls are provided with internal cooling and are arranged in a number of bearings, whose bearing height, taken from the center of the bearing in the direction towards the strand skin, is smaller than the radius of the roller body. The internal cooling is to be effected by a coolant pipe concentrically arranged in an axial bore of the roller body, whereby a coolant circuit is formed. Furthermore, each one of the rollers or rolls is to be directly driven in order to prevent individual rollers from coming to a stand-still in case of a distortion, from being warmed up unevenly and from being destroyed thereby.